High efforts are devoted to the study of 1D nanostructured material like nanotubes nanofibers and nanowires due to the unique physical and chemical properties associated with the structural confinements in nanoscale. However, from the engineering application point of view, separation and recovery is still a huge obstacle for these 1D nanostructured materials. Most recently, some efforts have been devoted to fabricated paper, sheet, membrane and other devices.
For example, metal oxide nanowires and carbon nanotubes have been organized into paper-like free standing membranes (FSM) for new applications (Yuan, J., Laubernds, K., et al., 2004, Adv. Mater., vol. 16, p. 1729; Endo, M., Muramatsu, H., et al., 2005, Nature, vol. 433, p. 476). However, a main problem of the materials obtained from nanostructured material remains their weak mechanical strength.
Dong, W., Cogbill, A., et al. (2006, J. Of Physical Chemistry B Letters, vol. 110, p. 16819) report a hydrothermal synthesis of TiO2-based long nanowire catalysts that have been directly cast into FSM-based paper and devices (e.g. tube, bowl, cup).
US 2006/0068668 A1 describes nanofiber filters supported by microfibers which are supposed to enhance the mechanical strength of the filters described in this US application.
Due to their weak uniformity the mechanical strength and pore size distribution of these membranes remain a need for further improvement.